1. Field of the Invention
The present invention relates to a vehicle electronic key system that controls a state of doors of a vehicle, such as a locked state and an unlocked state, based on a communication between a mobile unit and a vehicle unit.
2. Description of Related Art
A vehicle electronic key system is disclosed in an operation manual of a new model vehicle, which is published in Aug. 2000. The vehicle electronic key system includes a mobile unit having an electronic key and a vehicle unit. The vehicle electronic key system controls a state of doors of vehicles, such as a locked state and an unlocked state. The state of the doors is controlled based on a check result of an ID code of the mobile unit by communication between the mobile unit and the vehicle unit. The electronic key system also unlocks a steering lock and permits to start an engine when a user having the mobile unit is within a vehicle compartment.
In such an electronic key system, predetermined detection areas are formed inside and outside the vehicle. The vehicle unit transmits an interrogational signal at a predetermined time interval toward the detection areas. The electronic key system always monitors an approach of a user having the mobile unit, a ride on the vehicle, and getting out of the vehicle based on a response from the mobile unit in response to the interrogational signal.
In detail, when the user having the mobile unit approaches the vehicle to ride on the vehicle and then the user enters into the detection area, the mobile unit transmits an ID code to a receiver of the vehicle in response to the interrogational signal. The ID code transmitted from the mobile unit is checked in the vehicle unit whether the ID code corresponds to a registered ID code of the vehicle unit. When the ID code of the mobile unit corresponds to the registered ID code, a control unit of the vehicle unit sets doors to an unlock-standby state. Then, when the user having the mobile unit touches one of the doors in the unlock-standby state, the doors are unlocked in response to a detection of the touch via a touch sensor.
On the other hand, when the user having the mobile unit gets out of the vehicle after the engine is stopped, the detection area is shifted from the inside of the vehicle to the outside of the vehicle. When a door lock switch that is disposed near the door handle is operated when the detection area is formed outside the vehicle, the doors are locked.
In such a vehicle electronic key system, the user having the mobile unit can lock and unlock the doors without holding the mobile unit in hands. This improves convenience of the user.
However, the user cannot easily recognize the state of the door, such as the locked state, the unlocked state, and the unlock-standby state. For example, when the user having the mobile unit approaches the vehicle and then the user touches the door handle, the door is unlocked. However, the user cannot recognize that the door is in the unlock-standby state until the user touches the door handle. In addition, the user cannot easily check the unlocked state of the doors when the user operates the door lock switch.